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assumption the radiation from the producer becomes more nearly what would be expected, although a detailed comparison is useless owing to the confusing way in which von Jiiptner calculates the hydrogen on the basis of its full calorific value, including the latent heat of condensation. This has already been referred to at length in Chapter VIII.
It is possible that the fires were at a low temperature for a short time, but they could hardly be run continuously under such conditions. I have operated a fire for several hours at a black heat, but at the end of that time the whole top of the fire had become a bed of tar, so that it was impossible to do any poking, and it was necessary to stop charging fresh coal, decrease the amount of steam and allow the fire to burn up and break up the tarry matters.
It may appear at first sight that the presence of carbonic acid (C02) in the gas is the most important loss, but this item is taken care of under the head of sensible heat and under radiation; an excess of carbonic acid must give rise to heat and this heat must show itself somewhere. If it is used to dissociate steam then it is not lost, for the gas will be enriched by the hydrogen, consequently it is not entirely right to assume that a slight increase in carbonic acid means poorer practice. The gas above quoted as -made at Steelton ran as follows:
If less steam had been used the fire would have been hotter, and if properly poked would have shown a lower percentage of C02; but it would also have shown a lower percentage of H, so that nothing would have been gained in the calorific value of the gas, and the heat value of the coal would not have been better conserved.
TABLE IX-D. Value Represented by C02 in Gas.
2 p	jr ce	nt. C(	3a= 5.3 pc	r ce	at. lot
3 ' '			80		
4    '			10.8		
5			13.7		
6			16.6		
7			19.6		
8			23.0		
9			26.5		t
10			30.0		t